The filoviruses, Ebola (EBOV) and Marburg (MARV), cause periodic hemorrhagic fever outbreaks in sub- Saharan Africa. Because of the high rates of mortality associated with these infections and high transmissibility of these viruses in the human population, this family of viruses has been placed on the Category A select agent list that has been established by the Centers for Disease Control and Prevention. No anti-viral therapies are currently available against these viruses. While the development of a filoviral vaccine looks promising, immunity to any vaccine is not immediate. Recent studies suggest that reduction in virus load during the infection has a significant impact on deleterious outcomes. Thus, a transient reduction of virus load may be quite effective at decreasing mortality associated with filovirus infection. Here, we propose to develop an antiviral therapy that could be used to reduce virus load. We propose to select RNA aptamers against the coiled coil region of EBOV glycoprotein GP2 ectodomain. Aptamers are small oligonucleotides (generally 20- 50 bp) that specifically bind with high affinity to proteins or small target molecules, are not immunogenic and can be stabilized by chemical modifications for a longer in vivo half life. Aptamer binding to the carboxy terminal coiled coil region of EBOV GP2 would be predicted to prevent virus fusion with cellular membranes thereby inhibiting virus entry into permissive cells. Small inhibitors to the analogous region of the HIV-1 TM protein have proved highly successful at inhibiting HIV replication and these inhibitors are now part of the antiviral arsenal used against HIV-1 in the clinic. The EBOV glycoprotein GP2 will serve as an excellent target for aptamers because this region of the protein resides extracellularly on both virions and infected cells allowing aptamers ready access to the targeted region of the protein. Furthermore, the GP2 carboxy terminal coiled coil region (also called the heptad repeat region) is highly conserved across the four strains of EBOV and is believed to be unstructured and accessible in the pre-fusion GP structure. In Aim 1, we will select aptamers that bind to both a peptide derived from the GP2 carboxy terminal coiled coil region and to EBOV GP on the surface of virus like particles. In Aim 2, we will optimize and characterize the aptamer(s) that we select against EBOV GP2. We will then test the efficacy of the aptamers in blocking EBOV and MARV GP dependent transduction and EBOV infection. Development of aptamers that target EBOV GP2 and block virion entry will complement ongoing studies within the Maury laboratory that are actively selecting RNA aptamers against the EBOV GP1 receptor binding domain. The development of EBOV GP2 aptamers should prove highly successful in transiently reducing viremia in the infected individual. The use of antivirals against filoviruses as a stop-gap measure against sporadic outbreaks will be highly beneficial even if vaccine development is successful as it is unrealistic to believe that wide spread vaccination of African populations against these viruses will occur in the near future. PUBLIC HEALTH RELEVANCE: The filoviruses Ebola and Marburg cause devastating outbreaks of hemorrhagic fever and currently there are no antiviral therapies or vaccines available for these dreadful viruses. We propose to select small RNA aptamers that bind to Ebola glycoprotein 2 and prevent fusion of the virus with cellular membranes. The aptamers selected through these studies may serve as important antivirals to reduce mortality associated with these infections.